1. Field of the Invention
The present invention relates to a composite valve which is preferably used in a heat pump type cooling and heating system or the like, and more particularly to a composite valve which is provided with a pilot type large flow rate control valve and a small flow rate control valve.
2. Description of the Conventional Art
As a heat pump type cooling and heating system, there has been conventionally known a structure which is provided with a compressor, a condenser, an evaporator, an expansion valve and a four-way valve for converting (inverting) a refrigerant flow path.
On the other hand, as a heat pump type cooling and heating system for a vehicle (for example, for an electric vehicle), there has been proposed a system which does not invert a flow of a refrigerant and is provided independently with an expansion valve for cooling and an expansion valve for heating, for example, as shown in FIG. 1 of Japanese Patent No. 3799732.
The flow of the refrigerant is not inverted in the system mentioned above. Accordingly, for example, paying attention to an expansion valve for heating (reference numeral 24) shown in FIG. 1 of Japanese Patent No. 3799732, it is structured such that an electromagnetic valve for cooling (reference numeral 26) is provided in parallel with the expansion valve for heating, the electromagnetic valve for cooling is closed and the refrigerant is narrowed down by means of the expansion valve for heating at a time of heating, and the expansion valve does not carry out the narrowing down of the refrigerant by setting the electromagnetic valve for cooling open and bypassing the inlet and outlet of the expansion valve for heating at a time of cooling.
In the meantime, if the expansion valve and the electromagnetic valve for bypassing are respectively provided for cooling and for heating, the system is enlarged in size, a piping assembling cost or the like becomes high, and there is a risk that an electric power consumption is enlarged.
Accordingly, it is thought to achieve these functions by one electrically operated valve. In other words, for example, the refrigerant may be narrowed down by the electrically operated valve at a time of heating, and the electrically operated valve may be fully opened at a time of cooling.
In this case, a description will be given of one example of a conventional electrically operated valve with reference to FIG. 8.
An electrically operated valve 1′ in an illustrated example is provided with a valve shaft 25 which has a lower shaft portion 25a and an upper small diameter shaft portion 25b, a valve main body 40 which has a valve chamber 41, a can 60 which is bonded in a sealing manner to the valve main body 40 in its lower end portion, a rotor 30 (a rotating axis O) which is arranged in an inner periphery of the can 60 so as to be spaced at a predetermined gap a, and a stator 50A which is outward fitted to the can 60 so as to rotationally drive the rotor 30.
The valve shaft 25 is integrally provided with a valve body portion 44 having a specific shape (two stages of inverted circular truncated cone shapes respectively having predetermined angles of center) in a lower end portion of the lower shaft portion 25a, and the present electrically operated valve 1′ is structured such that a passing flow rate of the refrigerant is controlled by changing a lift amount of the valve body portion 44.
The valve chamber 41 of the valve main body 40 is provided in its lower portion with a valve seat 42 having a valve port (an orifice) 43 which the valve body portion 44 comes close to and away from, and is opened in its side portion to a first inlet and outlet 5′, and a lower portion of the valve main body 40 is provided with a second inlet and outlet 6′ so as to be connected to the valve port 43.
The stator 50A is constructed by a yoke 51, a bobbin 52, a stator coil 53, a resin mold cover 56 and the like, a stepping motor 50 is constructed by the rotor 30, the stator 50A and the like, and an elevation driving mechanism for regulating a lift amount (=an opening degree) of the valve body portion 44 with respect to the valve port 43 is constructed by the stepping motor 50, a feed screw (a female thread portion 38 and a male thread portion 48) mentioned below and the like.
A support ring 36 is integrally connected to the rotor 30, and an upper protruding portion of a lower opened and tubular valve shaft holder 32 which is arranged in an outer periphery of a guide bush 46 is fixed, for example, by caulking to the support ring 36, whereby the rotor 30, the support ring 36 and the valve shaft holder 32 are integrally connected.
Further, a lower end portion of the tubular guide bush 46 is pressed into and fixed to a fitting hole 49 which is provided in an upper portion of the valve main body 40, and the lower shaft portion 25a of the valve shaft 25 is inward inserted slidably to the guide bush 46. Further, in order to move up and down the valve shaft 25 (the valve body portion 44) by utilizing a rotation of the rotor 30, a male thread portion 48 is formed in an outer periphery of the guide bush 46, a female thread portion 38 is formed in an inner periphery of the valve shaft holder 32, and a feed screw is constructed by the male thread portion 48 and the female thread portion 38.
Further, an upper small diameter portion 46b of the guide bush 46 is inward inserted to an upper portion of the valve shaft holder 32, and the upper small diameter shaft portion 25b of the valve shaft 25 is inserted to (a through hole formed in) the center of a ceiling portion of the valve shaft holder 32. A push nut 33 is pressed into and fixed to an upper end portion of the upper small diameter shaft portion 25b of the valve shaft 25.
Further, the valve shaft 25 is outward inserted to the upper small diameter shaft portion 25b of the valve shaft 25, and is normally energized downward (in a valve closing direction) by a valve closing spring 34 constructed by a compression coil spring which is installed in a compression manner between a ceiling portion of the valve shaft holder 32 and an upper end terrace surface of the lower shaft portion 25a in the valve shaft 25. A restoring spring 35 constructed by a coil spring is provided in an outer periphery of the push nut 33 on the ceiling portion of the valve shaft holder 32.
To the guide bush 46, there is firmly fixed a lower stopper body (a fixing stopper) 47 which constructs one of rotation and downward movement stopper mechanisms for inhibiting a further rotation and downward movement at a time when the rotor 30 is rotated and moved downward to a predetermined valve closing position, and to the valve shaft holder 32, there is firmly fixed an upper stopper body (a movable stopper) 37 which constructs another of the stopper mechanisms.
In this case, the valve closing spring 34 is arranged for obtaining a desired seal pressure in a valve closed state in which the valve body portion 44 seats on the valve port 43 (preventing a leakage), and for reducing an impact at a time when the valve body portion 44 comes into contact with the valve port 43.
In the electrically operated valve 1′ structured as mentioned above, the rotor 30 and the valve shaft holder 32 are rotated in one direction with respect to the guide bush 46 which is fixed to the valve main body 40, by supplying an electrifying and exciting pulse to the motor 50 (the stator 50A) in accordance with a first mode, and on the basis of a screw feeding of the thread portions 48 and 38, for example, the valve shaft holder 32 moves downward, the valve body portion 44 is pressed to the valve seat 42, and the valve port 43 is closed.
At a time point when the valve port 43 is closed, the upper stopper body 37 has not come into contact with the lower stopper body 47 yet, and the rotor 30 and the valve shaft holder 32 further rotate and move downward while the valve body portion 44 closes the valve port 43. In this case, since the valve shaft 25 (the valve body portion 44) does not move downward, however, the valve shaft holder 32 moves downward, the valve closing spring 34 is compressed at a predetermined amount. As a result, the valve body portion 44 is strongly pressed to the valve seat 43, the upper stopper body 37 comes into contact with the lower stopper body 47 on the basis of the rotation and the downward movement of the valve shaft holder 32, and the rotation and the downward movement of the valve shaft holder 32 are forcibly stopped even if the pulse supply with respect to the stator 50A is thereafter carried on.
On the other hand, if the electrifying and exciting pulse is supplied in accordance with a second mode to the stator 50A from this fully closed state, the rotor 30 and the valve shaft holder 32 are rotated in a reverse direction with respect to the guide bush 46 which is fixed to the valve main body 40, and the valve shaft holder 32 moves upward this time on the basis of the screw feeding of the thread portions 48 and 38. In this case, since the valve closing spring 34 is compressed at the predetermined amount as mentioned above, at a time point of starting the rotation and the upward movement of the valve shaft holder 32 (a time point of starting the pulse supply), the valve body portion 44 is not disconnected from the valve seat 42 and remains in the valve closed state (a lift amount=0) until the valve closing spring 34 extends at the predetermined amount mentioned above. Further, if the valve shaft holder 32 is further rotated and moved upward after the valve closing spring 34 extends at the predetermined amount, the valve body portion 24 is disconnected from the valve seat 42 and the valve port 43 is opened, so that the refrigerant passes through the valve port 43.
In this case, it is possible to optionally and finely regulate the lift amount of the valve body portion 44, in other words, an effective opening area (=an opening degree) of the valve port 43 on the basis of an amount of rotation of the rotor 30. Further, since the amount of rotation of the rotor 30 is controlled by a supply pulse number, it is possible to control a flow rate of the refrigerant at a high precision.
Accordingly, in the case that the electrically operated valve 1′ having the structure mentioned above is employed as the electrically operated valve having both functions of the expansion valve and the electromagnetic valve for bypassing shown in the Japanese Patent No. 3799732, it is set to a maximum opening degree (a maximum lift amount) in such a manner as to reduce the pressure loss as much as possible so as to serve as the electromagnetic valve for bypassing, for example, at a time of the cooling operation, and it is set such as to finely control the opening degree (the lift amount) so as to serve as the expansion valve and finely control the valve opening degree, that is, the flow rate of the refrigerant, for example, at a time of the heating operation.
However, in the electrically operated valve 1′, an improvement of a flow rate control precision in the small flow rate region and an increase of a controllable flow rate come to an antinomy. In other words, in order to make the electrically operated valve 1′ serve as the expansion valve, it is necessary to secure a high flow rate control precision in the small flow rate region. Since it is demanded to make a resolving power of the flow rate control high for this purpose, it is necessary to make a valve bore diameter (an effective opening area) as small as possible. On the contrary, in order to make it serve as the electromagnetic valve for bypassing, since it is demanded to suppress the pressure loss as low as possible, the valve bore diameter can not be made so small (smaller than an effective passage cross sectional area of a piping system). In other words, if the valve bore diameter is made smaller, it is possible to make the flow rate control precision in the small flow rate region high, however, if it is intended to increase a flow rate (a controllable flow rate) of the refrigerant which is circulated to the system, the valve port portion comes to a resistance and the pressure loss is enlarged even if the valve opening degree is made maximum. On the contrary, if the valve bore diameter is enlarged, the increase of the controllable flow rate (the reduction of the pressure loss) can be achieved, however, the flow rate control precision in the small flow rate region is lowered. In addition, it is necessary to enlarge the valve body or the like in correspondence to the valve bore diameter, a great torque is necessary for driving the valve body, and there is a risk that an enlargement in size and an increase of an electric power consumption are caused.
Further, if the resolving power is made higher in order to achieve an improvement of the flow rate control precision in the small flow rate region (for example, the valve body lift amount per one rotation of the rotor is made smaller), it takes a long time to reach a full open state (a flow path bypass state) from the small flow rate control state, and an opening gap (a gap between the valve body portion and the valve port wall surface) at a time of the small flow rate control becomes very narrow, so that there is a risk that a foreign material or the like is bitten into the gap so as to be clogged.
Accordingly, in order to achieve both an improvement of a flow rate control precision and an increase of a controllable flow rate (a reduction of the pressure loss) in the small flow rate region, achieve a reduction of a time required for reaching the full open state from the small flow rate control state and achieve a reduction of an electric power consumption, Japanese Patent No. 4416528 discloses a provision of a pilot type first control valve (a first valve body and a first valve port) for a large flow rate and a second control valve (a second valve body and a second valve port) for a small flow rate, in more detail, a composite valve structured such as to open and close the first valve port having a large bore diameter by the piston type first valve body, open and close the second valve port having a small bore diameter by the needle type second valve body which is an independent body from the first valve body and is provided in the lower portion of the valve shaft (25), and make the second control valve for the small flow rate serve as the pilot valve of the first control valve for the large flow rate.
In this composite valve, when the lift amount of the valve shaft (the second valve body) is equal to or less than a predetermined amount (when the second control valve opening degree is equal to or less than a predetermined value), there is established a small flow rate control state in which the first valve body closes the first valve port, and the second control valve opening degree for the small flow rate is controlled by the second valve body. At this time, the refrigerant at an amount corresponding to the lift amount (the second control valve opening degree) of the second valve body flows to the inflow port→the first valve chamber→the gap of the sliding surface formed between the outer peripheral surface of the first valve body and the wall surface of the fitting and inserting chamber→the back pressure chamber→the pilot passage→the second valve chamber→the second valve port→the outflow passage→the outflow port. Further, if the lift amount of the valve shaft (the second valve body) goes beyond the predetermined amount, the amount of the refrigerant flowing out of the back pressure chamber via the second valve port is increased in comparison with the small flow rate control time, the pressure of the back pressure chamber is lowered, and the valve opening force becomes finally larger than the valve closing force acting on the first valve body, whereby the first valve body opens the first valve port, and there is established a large flow rate control state in which the refrigerant flows to the inflow port→the first valve chamber→the first valve port→the outflow port.
As mentioned above, it is possible to achieve both the improvement of the flow rate control precision in the small flow rate region and the increase of the controllable flow rate (the reduction of the pressure loss), and the low electric power consumption, by opening and closing the first valve port having the large bore diameter by means of the first valve body, opening and closing the second valve port having the small bore diameter by means of the second valve body, and making the second valve body serve as the pilot valve of the first control valve for the large flow rate.
However, in the composite valve described in the Japanese Patent No. 4416528, since the single second control valve for the small flow rate serves as the control valve for the small flow rate region and the pilot valve with respect to the first control valve for the large flow rate, there is a risk that the following problem is generated. In other words, since it is necessary to widely increase the flow rate of the refrigerant passing through the second control valve for the small flow rate in comparison with the small flow rate control time, in order to switch from the small flow rate control to the large flow rate control, it is necessary to set the bore diameter (the effective opening area) of the second valve port significantly larger than the bore diameter which is necessary for the small flow rate control. Accordingly, an increase of a motion load, and an enlargement in size of a driving portion (a motor portion) and a valve main body tend to be caused, and a dimensional and a shape of the second control valve for the small flow rate can not be set to those which are optimum for the small flow rate control, so that there is such a problem that a flow rate control precision at a time of the small flow rate control can not be enhanced very much.
Further, since the opening and closing of the first control valve for the large flow rate depends on the lift amount of the second valve body changing subtly, there is not a little a case that the opening and closing of the first control valve for the large flow rate is not carried out at a desired timing. Further, since the refrigerant is circulated via the sliding surface gap of the first valve body→the back pressure chamber→the pilot passage at a time of the small flow rate control, there is such a problem that a malfunction caused by a small foreign material mixed into the refrigerant (for example, the locking of the first valve body caused by the biting of the small foreign material into the sliding surface gap) tends to be generated.
Accordingly, in order to overcome the above mentioned problem, the inventors of the present application has previously proposed the composite valve as described in Japanese Patent Application No. 2011-68451 filed on March 25 (corresponding to U.S. patent application Ser. No. 13/423,490 filed on Mar. 19, 2012, claiming priority of the Japanese Patent Application No. 2011-68451). The composite valve is provided with a piston type first valve body, a valve shaft provided with a needle type second valve body, an elevation driving means for moving up and down the valve shaft, a pilot valve body driven so as to be opened and closed by utilizing the elevating motion of the valve shaft, and a valve main body provided with an inflow port and an outflow port, and is structured such that between the inflow port and the outflow port in the valve main body, there are provided a fitting and inserting chamber to which the first valve body is slidably fitted and inserted, and which is zoned into a back pressure chamber and a first valve chamber by the first valve body, a first valve port which is open to the first valve chamber, a second valve chamber in which the pilot valve body and the second valve body are arranged so as to be movable up and down, a second valve port which communicates the inflow port or the first valve chamber with the second valve chamber, and a pilot passage which communicates the back pressure chamber with the second valve chamber, and such that in the case that a lift amount of the second valve body is equal to or less than a predetermined amount, the pilot passage is closed by the pilot valve body, and the first valve port is closed by the first valve body, thereby taking a small flow rate control state in which a flow rate is controlled in correspondence to the lift amount of the second valve body, and in the case that the lift amount of the second valve body goes beyond the predetermined amount, the pilot valve body is moved up in conjunction with the upward movement of the valve shaft so as to open the pilot passage, thereby taking a large flow rate control state in which the first valve body opens the first valve port on the basis of this. In this composite valve, an actuator for moving up and down the valve shaft 25 as described with regard to FIG. 8 can be used as an elevating means of the valve shaft which is provided with the second valve body.
In the proposed composite valve mentioned above, the second valve body for the small flow rate control is provided independently from the pilot valve body for driving the first valve body for the large flow rate control, the second valve body carries out the small flow rate control until the second valve body lifts up at a predetermined amount, and the pilot valve body is drawn up at a state that the second valve body lifts up at the predetermined amount so as to drive the first valve body. Accordingly, it is possible to set the dimension and the shape of the second control valve for the small flow rate (the second valve body) so as to be optimum for the small flow rate control, and it is possible to securely carry out the opening and closing of the first control valve for the large flow rate (the first valve body) at a desired timing. Further, there can be achieved such an excellent effect that it is possible to make the malfunction hard to be generated.